Assuming you mean Essex state schools 11 plus (CSSE) - there is no NVR. The papers are VR, Maths and English.
The past real VR papers cannot be purchased. A single sample paper is available from the CSSE along with the last 2 years Maths and English papers.
GL assessment sell sample papers of the same type as do other companies listed in the above link. Any resources used need to be those covering the "21 type" VR questions.
Suitable types in link below (it originates in the bucks forum but also applies to essex)http://www.elevenplusexams.co.uk/forum/11plus/viewtopic.php?f=12&t=4782